LY309887 is an inhibitor of the enzyme glycinamide ribonucleotide formyltransferase, which is involved in de novo folic acid synthesis. The purpose of the phase I study is to determine the MTD of LY309887 as a single dose given IV once every 21 days with folic acid supplementation given orally 2 days before, on the day of, and for 2 days after administration.